Calculators / Pool
Pool salt calculator: how much salt to add?
Test your salt, then put in the pool size. You'll get the pounds and bags to get your cell where it wants to be.
Updated · How we check our numbers
Add this much
121 lb of salt
That's 4 bags at 40 lb to take 18,193 gallons from 2,400 to 3,200 ppm.
- Pool
- 18,193 gal
- Salt now
- 2,400 ppm
- Target
- 3,200 ppm
- 40 lb bags
- 4
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Estimate for planning only, not professional advice. Check the manufacturer’s instructions, your local code and a licensed professional before you buy, build or install. Use at your own risk. Terms.
surface = 32 ft × 16 ft = 512 sq ft
average depth = (3.5 + 6) ÷ 2 = 4.75 ft
gallons = 512 sq ft × 4.75 ft × 7.48 = 18,193 gal
ppm to add = 3,200 − 2,400 = 800
salt = 18,193 gal × 800 ppm × 8.34 ÷ 1,000,000 = 121.4 lb
bags = 121.4 ÷ 40 = 4, rounded up
Turn the cell off, pour the salt around the shallow end with the pump running, and brush it so it doesn't sit on the floor.
Give it 24 hours to dissolve and mix before you test again or turn the cell back on.
Use pool salt, 99% or better sodium chloride. No rock salt, no salt with anti-caking agents, no iodized salt.
How we work it out
Water weighs 8.34 lb a gallon. One part per million of salt in a gallon is 8.34 millionths of a pound, so the math is short.
salt (lb) = gallons × ppm to add × 8.34 ÷ 1,000,000
bags = salt ÷ 40, rounded up
Fresh water to 3,200 ppm takes about 267 lb per 10,000 gallons. Hayward cells run 2,700 to 3,400 ppm. Pentair IntelliChlor runs 3,000 to 4,500 with 3,400 ideal. Salt doesn't evaporate, so if you overshoot, the only fix is draining some water and refilling.
Where the numbers come from
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